1. Field of the Invention
The present invention relates to an organic light emitting diode (OLED) display device.
2. Description of the Related Art
In general, flat panel displays (FPDs) are being used in place of cathode ray tube (CRT) displays because the FPDs are thinner and lighter. Typical examples of the FPDs include liquid crystal displays (LCDs) and organic light emitting diode (OLED) display devices. OLED display devices have a higher luminance and a wider viewing angle than LCDs. Also, OLED display devices require no backlight, and thus, may be ultrathin.
In an OLED display device, electrons emitted from a cathode recombine with holes emitted from an anode in a thin organic layer to form excitons. When the excitons transition from an excited state to a ground state, light with a specific wavelength is emitted. In order to facilitate the emission of the light by the recombination of the electrons with the holes, the anode, into which the holes are injected, may be formed of a material having a large work function, while the cathode, into which the electrons are injected, may be formed of a material having a small work function.
However, since the cathode may be highly active and chemically unstable, the cathode may react easily with external oxygen or moisture, and thus may be susceptible to oxidation or corrosion. Also, the thin organic layer may be crystallized due to a reaction with external moisture or oxygen so that the organic layer may be structurally changed and have degraded emission characteristics.
Thus, various methods for encapsulating OLED display devices have been developed in order to block oxygen and moisture from infiltrating OLED display devices. Among these, an encapsulation method using an encapsulation substrate has lately attracted considerable attention.
According to the encapsulation method using the encapsulation substrate, a bonding member may be interposed between a base substrate, on which OLEDs are formed, and the encapsulation substrate, and pressure may be applied to bond the base substrate to the encapsulation substrate.
However, since the base substrate is pressure bonded to the encapsulation substrate, the bonding member may flow out of a bonding region according to the amount and pressure applied to the bonding member. As such, controlling the width of the bonding member becomes problematic. In addition, when an amount of pressure is controlled to prevent the bonding member from flowing out, the thickness of the bonding member may be increased or become non-uniform.